The present invention is very adaptable to provide either mechanical or electrical power in both stationary and mobile systems. The preferred embodiments, however, are intended for use in mobile systems, such as in the powering of automobiles, trucks and other vehicles. As such, the prior art relating to power plants for such mobile systems and the fuels used therein will be discussed, it being understood however, that the present invention is not so limited in its application.
At the present time, a very large majority of vehicles in day-to-day operation contain internal combustion engines operating on some suitable hydrocarbon fuel. Of these, most operate on gasoline, while smaller numbers operate on diesel fuels and liquid propane. These fuels, however, are becoming increasingly expensive, are subject to supply limitations by foreign powers, and would appear to be nearly exhaustible in supply in the not too distant future. Accordingly, it would be desirable to develop other propulsion systems based on other fuels or other sources of energy more readily available and not as subject to control by foreign powers.
One type of propulsion energy which attracted considerable interest in the early days of automobiles, and is the subject of substantial study at the present time, is electricity. However, since the early efforts, the rate of advance of the energy storage (battery) technology has been disappointing, and electric powered cars operating on batteries are currently highly limited in range and in recharging rate in comparison to the range of hydrocarbon fuel vehicles and the speed with which they may be refueled. Vehicles powered with electricity, however, have the advantage that the original or primary source of energy used to charge the batteries may be substantially anything, hydro-electric plants, fossil fuel burning plants, and nuclear power generating plants being the most common. Obviously, even solar energy is a potential source of power to recharge the batteries.
Other fuels have also been considered for use in vehicles, including hydrogen and acetylene. Hydrogen has the advantage of almost unlimited supply from water, and has a high energy content on a per pound basis, though poses difficult storage problems and substantial safety hazards. In essence, the concept is to use hydrogen as an energy containing medium for burning in a vehicle, thereby creating water vapor in the exhaust. The hydrogen would be generated at some remote power plant using coal, nuclear or other sources of energy, probably by the decomposition of water at that location. Such use of hydrogen as a fuel, however, has in general not proceeded beyond the very early experimental stages.
Acetylene, as previously mentioned, has also been proposed for use as a fuel for internal combustion engines. On a per pound basis, acetylene has a high energy content (higher than gasoline) and forms an explosive mixture with air over a wide range of mixing ratios. It also may be generated relatively easy from calcium carbide, a material which in itself is relatively safe and easily handled until mixed with water. As such, the safety hazard of carrying calcium carbide in a vehicle is probably substantially less than that of carrying gasoline, liquid propane or other fuels in their combustible state.
One prior art system for utilizing acetylene as a source of fuel in a mobile system is disclosed in U.S. Pat. No. 3,664,134. In that system, calcium carbide and water are combined in a reactor to form acetylene, which is then used as a fuel for a conventional internal combustion engine. The system of that patent also features as afterburner, and a calcium hydroxide scrubber for the engine exhaust for reduction of atmospheric pollutants. This system has the advantage of being operative with a conventional internal combustion engine; however, the acetylene generator has certain inefficiencies, in that apparently a large excess of water is required in the wet process for generating acetylene in the reactor in order to keep the reactor temperatures down. More importantly, all of the heat given off in the exothermic reaction between the calcium carbide and the water is lost, as there is no way to recover this heat in any useful manner for the system disclosed.
Another prior art system for utilizing acetylene as a source of fuel in a mobile system is disclosed in U.S. Pat. No. 4,257,232. This system passes the feedwater through the reactor to cool the reactor and preheat the feedwater before delivering the feedwater to the boiler. While this recovers heat given off in the exothermic reaction between the calcium carbide and the water, energy is lost in the exhaust of the burner that heats the boiler, in the condensation of the exhaust steam and water from the steam expander, and in the dissociation of hydrogen and oxygen in the steam expander.